The present invention relates to an empirical electrical method for remote sensing of steam quality utilizing flow-through grids which allow measurement of the electrical properties of a flowing two-phase mixture.
The measurement of steam quality in the oil field is important to the efficient application of steam assisted recovery of oil. Because of the increased energy content in higher quality steam it is important to maintain the highest possible steam quality at the injection sandface. The effectiveness of a steaming operation without a measure of steam quality downhole close to the point of injection would be difficult to determine. Therefore, a need exists for the remote sensing of steam quality.
A number of methods currently exist for the measurement of steam quality. For example, a December 1981 publication by Sandia National Laboratories, SAND80-7134, contains an article by A. R. Shouman entitled "Steam Quality Measurement: A State of the Art Review". Shouman reviewed existing methods and identified two techniques which could be useful for remote sensing of pure steam, one based on acoustic propagation characteristics of two-phase flow and a second on venturimeters.
Another method is disclosed by H. A. Wong, D.S. Scott, and E. Rhodes in an article "Flow Metering in Horizontal Adiabatic Two-Phase Flows" found in Flow/81: Its Measurement and Control in Science and Industry, Vol. 2, 1981, pp. 505-516. Wong et al. have developed a twisted tape venturimeter for two-phase quality measurements. Although this method has been used for steam quality measurements in the field, no detailed calibration measurements on wet, high pressure steam have been reported.
A venturimeter/orifice plate system has been used successfully (although not downhole) for wet steam quality measurements at up to 980 pounds per square inch (psi) by D. B. Collins and M. Gacesa as described in the March 1971 publication of J. Basic Engineering on pp. 11-21.
Other more recent techniques of steam quality measurement include gamma and x-ray attenuation. In order to be useful however, they require extensive calibration against known standards over the complete range of conditions which may be encountered downhole.
Therefore it is desired to provide an empirical electrical method for the remote sensing of steam quality that can be adapted to downhole steam quality measurement.